1. Field of the Invention
The present invention relates to a heavy duty tire in which rolling resistance can be reduced while keeping wet grip performance.
2. Description of the Related Art
By the request of energy-saving in recent years, a pneumatic tire with low rolling resistance is required to improve fuel efficiency of passenger cars. Generally, half amount of rolling resistance of tires depends on energy losses caused by deformation of rubber components in tires. Accordingly, in order to prevent a large deformation in a tread portion of a pneumatic tire, it is proposed that reducing the volume of a crown main groove and a shoulder main groove which continuously extend in the tire circumferential direction. Since the tire above has a high compression resistance in the tread portion as to prevent a large deformation, rolling resistance can be reduced.
However, the tire above tends to have low drainage performance, and thereby the wet grip performance can be deteriorated. As previously mentioned, rolling resistance and wet grip performance are in the relation of antinomy.
For improving such antinomy, there is proposed for example Japanese Patent laid open No. 2006-111091, wherein a heavy duty tire with a specified relation between a land ratio of a tread portion and a circumferential rigidity of a block row in a heavy duty tire is proposed.
However, further improved tire is required by the request of energy-saving in recent years.
It is an object of the present invention to provide a heavy duty tire in which rolling resistance can be reduced while keeping wet grip performance.